Device with simple DAC?

Hi there,

I know that this is somewhat off-topic here, but not completely :)

I intend to get some mini-boxes

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for an embedded Linux Project.

The device gives me all I need except a simple (slow 25HZ) DAC.

All I need is an Output Voltage between 0 and 5 Volts which could be controlled by means of some simple commands.

Do you have any recommondations for this? Some simple schematics are fine as well as the alternative would be a generic IO-Device like the Labjack U12

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Reply to
Sven Geggus
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Reply to
Rick Farmer

If you can live with a lower update rate, One way is to do a PWM output from the parallel port bits and then RC-filter the outputs. This will give you multiple (12?) possible DACS. The PWM can be done as part of the tic clock interrupt. One trick needed to get reasonable response time/ripple is to interlace the PWM.

Imagine a 8 bit PWM, one way to do 128 (50% duty cycle) is 128 cycles on and 128 cycles off but this has a low ripple frequency. A better way is to do one cycle on and one cycle off for all 256 cycles, thus having a higher ripple frequency - faster time constant filter - faster response time...

One simple way to generate interlaced PWM is by bit reversing the PWM reference count before it is compared with the PWM value...

Peter Wallace

Reply to
Peter Wallace

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